Re: AVR32 architecture patch against Linux 2.6.18-rc1 available

Haavard Skinnemoen
2006-07-06T18:48:40Z

On Thu, 06 Jul 2006 15:34:52 +0100
David Woodhouse <dwmw2@infradead.org> wrote:

> On Thu, 2006-07-06 at 16:13 +0200, Haavard Skinnemoen wrote:

> > As I understand it, though, drivers/dma is mostly for
> > memory-to-memory to transfers, while what I really need is
> > memory-to-hardware and hardware-to-memory transfers.
>
> With MMIO those are just a not-so-special case of memory-memory,
> surely? If the new framework doesn't support that, it probably
> _should_.

Yes, but there are at least two important differences:

* Hanshaking. The DMA controller must know when the peripheral has
new data available/is able to accept more data. Thus, you need to
specify which set of handshaking signals to use as well as which
direction the data is moved.
* One of the pointers often stays the same during the whole transfer.

I'm willing to give the drivers/dma framework a try, though, when the
time comes to forward-port the drivers that need such infrastructure.

Håvard